The Police’s obsession anthem “Every Breath You Take” was the biggest Billboard chart hit of 1983, and it later formed the basis of Puff Daddy’s “I’ll Be Missing You,” one of the biggest Billboard chart hits of 1997. It’s one of the biggest pop songs of all time, and its creation is etched into music-business legend. Today, for the first time, we get to hear a crucial document of how the song came into being.

Sting wrote “Every Breath You Take” at James Bond creator Ian Fleming’s Goldeneye resort in Jamaica. In October 1982, he recorded a solo demo of the song at London’s Utopia Studios, using a keyboard and drum machine rather than his Police bandmates. Later on, the Police tried recording different versions of the track before Sting’s bandmate Andy Summers came up with the track’s glimmering, arpeggiated guitar line. That guitar part is essential to the song’s success — it’s one of the key elements used in “I’ll Be Missing You” — but it didn’t earn Summers a songwriting credit for the track.

Sting’s solo demo version of “Every Breath You Take” went unreleased for decades, but it’s finally coming out now, thanks to an upcoming box-set edition of Synchronicity, the Police’s final album. Today, that demo arrives online, and we all get to compare and contrast. It’s striking how much of “Every Breath You Take” was already in place on the demo, but it’s even more striking to hear how empty the song sounds without that guitar part. If Summers had never come up with that part, “Every Breath You Take” might’ve been a hit, but it’s impossible to imagine it becoming the blockbuster that it was. Below, listen to the newly released demo and check out the Police’s original video.

The box-set version of Synchronicity is out tomorrow.